Radio communications are a pervasive part of modern society. For many, the availability of radio communication systems through which to communicate is a necessary aspect of daily life. Radio communication systems are constructed that provide both radio broadcast services as well as interactive, two-way communication services. Various radio communication systems are operable over wide areas, and others are operable over only local areas.
Cellular communication systems are amongst the radio communication systems that are widely used by many. The network infrastructures of cellular communication systems have been deployed over significant portions of the populated areas of the world. A subscriber to a cellular communication system generally subscribes for service to communicate by way of the network infrastructure of the associated communication system. Communications are generally effectuated through use of a mobile station, typically a portable, radio transceiver oftentimes of small physical dimensions permitting their hand-held operation and carriage. With continued advancements in circuit technologies, increasing functionality is able to be provided in circuitry of increasingly miniaturized dimensions. While early-generation, cellular communication systems and their associated mobile stations were used primarily for voice services, newer-generation, cellular communication systems, and their associated mobile stations, are permitting of increasingly data-intensive communication services. Different ones of the cellular communication systems operate at different frequency bands. For instance, the GSM (Global System for Mobile communications) 800 system operates at a frequency band defined between 824 and 894 MHz. The GSM 900 system operates at a frequency band extending between 890 and 960 MHz. The DCS (Digital Communication Service) system operates at a frequency band extending between 1710 and 1880 MHz. The PCS (Personal Communication Service) system operates at a frequency band extending between 1850 and 1990 MHz. The UMTS (Universal Mobile Telephone Service) operates at a frequency band extending between 1900 and 2200 MHz.
Other types of radio communication systems are also widely used. Some of such other systems share some of the aspects of cellular communication systems, or provide for interworking communications therewith. For instance, Bluetooth and WLAN (Wireless Local Area Network) communication systems provide for voice and data communication services, typically over relatively shorter ranges than the ranges over which cellular communication systems operate. Such systems are operable, e.g., in conformity with operating specifications set forth in the IEEE802.11b/g family of standards. And such systems are operable, for instance, at a frequency band located at the 2.4 GHz band. WLAN 802.11j/a systems are operable, for instance, at the 4.9-5.0 GHz, 5.15-5.35 GHz frequency band, or the 5.725-5.875 GHz frequency band. And, a GPS (Global Positioning System) radio broadcast system provides positioning services through the broadcast of signals at the 1.57 GHz band.
The various communication systems are not necessarily co-extensive. That is to say, the network infrastructures of some of such systems are deployed in some geographical areas and not others. And, in other geographical areas, other networks are deployed. Dual-mode, tri-mode, and quad-mode mobile stations are available that are permitting of their operation with two, three, and four different types of radio communication systems, respectively. Advancements in circuit technologies have permitted circuitry miniaturization that, in significant part, has permitted the multi-mode, mobile station implementations.
A challenging aspect of such multi-mode, mobile station implementations pertains to the antenna structures that transduce signal energy during the mobile-station operation. An antenna is typically of a length that is associated with the wavelengths of signal energy that is to be transduced. As noted-above, the different communication systems are operable at disparate frequency bands. As the mobile stations are increasingly packaged in small-sized housings, multi-mode devices that require antennas operable at multiple frequency bands must also be of dimensions to permit their positioning at the housing of such mobile stations.
Use of multiple antennas that operate at the different frequency bands of the multi-mode, mobile station increasingly become an impractical solution as the housing dimensions do not permit positioning of many antennas therein. PIFAs (Planar Inverted F Antennas) are sometimes used. PIFAs are compact, of low profiles, and are manufactured relatively easily. But, a PIFA is typically operable over only a narrow bandwidth. While the bandwidth of a PIFA can be increased by combining the PIFA structure with another broadband technology, such as a 3D multi-layered structure, such a combination negates, in significant part, the size advantages provided by a PIFA.
A need continues, therefore, to provide an antenna of small dimensions and capable of transducing signal energy of frequencies of multiple, disparate frequency bands.
It is in light of this background information related to antennas for radio devices that the significant improvements of the present invention have evolved.